Insect reproduction is of critical importance to human health because insects are a major vector of infectious human diseases. Many factors influence the timing and amount of investment in egg production by female insects. In many insect species, proteins (called "Acps") transferred from male to female in the seminal fluids induce females to increase egg production rate. Investigation into the mode of action of these proteins can provide insights into the molecular cascade that stimulates insect ovulation and aid in the development of methods to control reproduction of insect vectors of human disease. Drosophila melanogaster provides an excellent model system in which to study the mode of action of these proteins because D. melanogaster Acps have molecular counterparts in other insects (69% are found in Anopheles gambiae) and because an extensive set of molecular techniques has been developed for use in this species. I will investigate the mode of action of an ovulation-stimulating prohormone, Acp26Aa. The specific aims of my study are to (i) identify the site(s) of action of Acp26Aa; (ii) test whether processing is necessary for it to function; and (iii) determine which male- and female-derived molecules are involved in Acp26Aa activation. [unreadable] [unreadable]